Week 3 of the preseason is when teams get a chance to look at their starters the most during the game. Unless you're the Philadelphia Eagles, few major starters have played more than a half of football.

The Broncos are no different. Last week, they played the starters into the second quarter before looking at their backups.

One thing that'll be interesting in this last dress rehearsal for the Broncos' starters will be their opponent. They are facing the league's best defense in the San Francisco 49ers.

There are still a lot of questions to be answered from the Broncos offense and defense and this is the ultimate test during preseason. The question will come whether head coach John Fox plays his starters the expected three quarters of football, especially Peyton Manning.

All eyes will be on No. 18, but here are others that should be watched for.

Denver's Offensive Line

Ron Chenoy-US PRESSWIRE

In their short stint together, they have looked good. Manning has only taken one big hit while he was behind them, but this is the first time the outside world can see how good the Broncos offensive line is.

The 49ers are no slouch on defense and will bring it every down. They are relentless when it comes to pressuring the quarterback. Last season, they racked up 42 sacks. including 14 from rookie linebacker Aldon Smith.

Along with Smith, Justin Smith is one of the best defensive linemen in football and Patrick Willis is a top-10 player at middle linebacker.

Protecting Manning from these guys will be the key. Also, they will have to find a way to run block better for Willis McGahee and company.

It will be interesting to see if the starting line can mesh even more with additional time. What better way to learn what you have up front than against the 49ers' defense?

Derek Wolfe

Wolfe has been outstanding so far in two preseason games. He has recorded seven total tackles, five of which were solo. He also has two sacks and a couple of hits on the quarterback.

That's exactly what the Broncos were hoping to get from Wolfe when they took him in the second round, their first overall pick, out of the University of Cincinnati.

Wolfe will see even more time this week and his production should look even better playing longer minutes with Pro Bowl players Elvis Dumervil and Von Miller.

There's little doubt that Wolfe will be in the starting lineup for the Broncos once the regular season comes around. If he can have another strong game, then there will be no doubt of his place on the defense.

Denver's Running Backs

It's early, I know. But Denver's run game has been nonexistent and McGahee has had little success when he's been in.

In his 12 carries during the first two games, he's tallied just 44 yards (3.6 yards-per-carry) and one touchdown.

The number of carries is respectable, but coming off of a year when he rushed for 1,199 yards, the expectations are higher.

Especially with Manning at quarterback, McGahee needs to be that guy who can pile up yards on a small amount of carries.

If he can have a bigger game against San Francisco, it could propel him into the regular season when they face another stout defense in Pittsburgh in Week 1.

But it's not just McGahee who has low numbers. As a team, the Broncos have had 52 carries for 194 yards (3.7 average) and three touchdowns. The biggest problem so far has been the explosiveness of the backs. In two games, the Broncos haven't had a run longer than 13 yards. That has to change if the Broncos want to be successful.

It won't be easy against the 49ers defense, but a strong showing would go a long way for a corps that hasn't been all that great.

Denver's Run Defense

For a long while, the weak point in the Broncos defense has been its inability to stop the run. During the first two preseason games, they have given up 264 yards and over four yards per carry.

I'm not going to say their run defense isn't great; it just needs work. Seattle torched them for 228 yards in Week 2.

Denver fans are hoping that teams will be forced to throw more often now that Manning is running the offense and hopefully putting up more points. But you can't overlook the run defense. Especially when the AFC West is one of the best at running the rock.

Kansas City is a run-heavy team with Jamaal Charles and Peyton Hillis leading the way. San Diego won't put it on the ground as much, especially with Ryan Mathews getting injured. And if Darren McFadden can stay healthy, the Oakland Raiders will rely on him torch defenses.

This week, however, will be a great test for the Broncos run defense. The 49ers were eighth in the league last year, rushing for 127.8 yards per game. Led by Frank Gore, the 49ers run game could easily give the Broncos a headache.

If the Broncos can hold the 49ers to a manageable number of yards, they will be able to believe that they can slow down most teams in the NFL.

I doubt Harbaugh is holding a grudge about the decision, but he could send a couple extra blind-side blitzes to keep Manning uneasy.

On the blitzes that do come, Manning will have to feel them and get the ball out in a hurry. Everybody knows that the 49ers will be coming after Manning because it's their style of play.

The key for Manning is to get hit as well. He took a big hit last week, but the more he gets hit, the more he will feel comfortable and forget about his neck surgeries.

Manning has performed to an "eh" standard. But it's preseason so the fact that he has thrown three interceptions shouldn't be blown out of proportion. He is still getting his feet wet and each week is a huge test.

This week, Manning will get a chance to play into the third quarter. The Broncos will hope he can improve and lead the Broncos offense down for a couple of scores or at least find some rhythm with his wide receivers.

It's crazy that some people in the media are saying Manning shouldn't play that long. It's only preseason, so why risk it? I say let him play with his starting unit and take a hit or two. Let him know for sure he is okay to play and have no doubt he can play at an elite level.

Now if he takes too many hits early, then pull him because it is just preseason. But one or two hits? Let's see how Manning reacts to them.